In a multi-display system constituted by combining a plurality of display devices, when a control program (firmware) is updated for each display device, a rewrite process is required for the number of display devices, and an update time becomes long. Therefore, a technique of rewriting the control program held by each of the plurality of display devices constituting the multi-display system, collectively in a short time by an external device is known (for example, see Patent Document 1).
Moreover, at the time of installing the multi-display system, there may be a combination of the display devices in which versions of the firmware of the display device are not the same. Furthermore, in the maintenance of the multi-display system during operation, the display devices having a different firmware version may be mixed. In such a case, by applying a technique described in Patent Document 1, the newest firmware can be transferred to a plurality of display devices from an external device such as a personal computer, so that the firmware is rewritten in the respective display devices.